I think it looks great!
The motherboard looks like it's resting on top of some aluminum (?) pegs. Did you make those or buy them?
Thanks

I buy them, they are for electronics (not PC), I actually had them from a previous project

they are quite expensive, like 0,4 U$D each.
1 Gh/s sounds low for four 7850s. I have two 7850s, one gets 320Mh/s at 1050 and the other gets 350Mh/s at 1150. Are you running at stock?
Yes I know

, I am runing at stock (860 Mhz) I will love to get more juice from them, but i don't want to destroy any, GPU's are expensive here and have no warranty in my country.
The hottest card (the one closest to the PSU) runs at 60 C, so I think that i am ok with the temperature so far, but not sure how safe will be to OC them.
best technique is to underclock the memory a bit, as that reduces the heat production and is uneccessary to mining, and increase the core speeds slightly. If noise is not as issue, you can manually increase the fan speed setting as well to get a few degrees drop to temps. So long as the card runs smoothly and at a constant temperature and load, up to 65C is not an issue. (some drive thier cards up close to 80C, but that is risky IMO for the reasons you mentioned)